Typically weighing less than 35 pounds, the wolverine is the largest member of the weasel family Mustelidae.
They are powerfully built and have short legs with wide feet for traveling across the snow. These animals are a vital part of ecosystems in northern climes, and a great ambassador of the wild places they inhabit and the melting snow they require.
The species is rare, and faces significant challenges to its future in the U.S. Yet, because of their limited numbers, huge individual territories, and remote locations, it is difficult to gather data on wolverines and this poses a challenge to scientists, agencies, and others trying to understand wolverines’ habitat requirements and threats to their survival.
Wolverines have yet to be federally protected under the Endangered Species Act.
Defenders and our colleagues have been fighting for two decades to federally protect wolverines in the lower 48 states, where climate change threatens their future.
We filed a petition with the U.S. Fish and Wildlife Service (FWS) in 2000 requesting protection for the species under the ESA, and took legal action in 2005 and 2008 when the agency did not move forward to protect the species. In 2010, the FWS determined that wolverines did in fact warrant protections under the ESA, but the agency was unable to take further action until higher priorities were addressed. Then in 2011, FWS agreed in a multi-species legal settlement that wolverines in the contiguous U.S. would be reconsidered for listing. In February 2013, the FWS finally proposed to protect wolverines in the contiguous U.S. as a threatened species under the ESA. As of 2019, the final listing decision still has not been made.
Defenders recruits and trains volunteer “community scientists ” to document wolverines in the West using snow-tracking, hair (DNA) collection and remote cameras. We also reach out to backcountry recreation enthusiasts to document information whenever they see wolverines or their tracks. These data points can help provide scientists with important information about the location of wolverines.
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Threats to wolverines include habitat loss and fragmentation, climate change and some hunting.
Endangered Species Act
IUCN Red List
The wolverine is proposed for listing under the Endangered Species Act as threatened.
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Wolverines in the Lower 48 live in rugged, remote country, spending most of their time in high elevations near or above timberline. Further north in Alaska and Canada, wolverines occur within a wide variety of elevations in alpine, boreal and arctic habitats, including boreal forests, tundra and western mountains. Today, wolverines in the Lower 48 can be found in portions of the Northern Cascades in Washington and the northern Rocky Mountains in Montana, Idaho and Wyoming.
The estimated population in the lower 48 is around 300.
Wolverines do not hibernate and are well-adapted for winter existence, with extremely dense fur, large snowshoe-like paws that allow them to stay on top of deep snow, and crampon-like claws that enable them to climb up and over steep cliffs and snow-covered peaks.
Female wolverines give birth in winter in dens that provide security and a buffer to cold winter temperatures. These dens are generally tunneled through snow and are associated with uprooted trees, avalanche debris, and boulders, often in remote alpine cirques at or above tree line. Young wolverines are called kits, and are born white as snow.
Mating Season: Late spring to late summer
Gestation: Egg implantation is delayed until the following winter or spring, followed by a 30 to 45-day gestation period.
Litter Size: 1 - 5 kits, with an average in North America of 1 - 2 kits
Wolverines are opportunistic feeders and eat a variety of foods depending on availability. In the winter they primarily scavenge dead animals, while in the summer their diet consists mainly of smaller mammals such as porcupines, hares, marmots and ground squirrels. They can also take down much larger animals, including caribou and moose, when circumstances such as deep snow are in their favor.